Tubular insulator



Aug. 19, 1941. w BURLESQN 2,253,264

TUBULAR INSULATOR Filed March 1, 1940 I IIIIIIIIII,

:1 9 E/IIIIIIIII II I INVENTOR Wade //.Bur/esor1 BY au/ g ATTORNEY Patented Aug. 19, 1941 zcsazai TUBULAR msum'ron Wade H. Burleson, Mansfield, Ohio, aaaignor to The Ohio Brass Company, Mansfield, Ohio, a

corporation of New Jersey Application March 1, 1940, Serial No. 321,681

Claiml.

This invention relates to electric insulators, particularly of the post type, and has for one of its objects the provision of a tubular insulator which will be comparatively simple and economical to manufacture and in which the manufacturing losses will be reduced to a minimum.

A further object of the invention is to provide a tubular insulator in which danger of discharge through the central opening is avoided.

A further object of the invention is to provide a tubular insulator which is completely sealed, after the insulator is fired, and in the opening of which a dielectric medium is disposed to eliminate danger of discharge through the interior of the insulator.

A further object of the invention is to provide a device of the class named which shall be of improved construction and operation.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanving drawing and described in the following specification and it is more particularly pointed out in the appended claims.

In the drawing:

Fig. 1 is a vertical sectional view of a tubula insulator showing one embodiment of the present invention.

Figs. 2 and 3 are fragmentary sectional views showing modified forms of the invention.

Fig. 4 is a vertical sectional view of another modification of the invention.

Figure 5 is a sectional view of another modification of the invention.

Considerable difliculty has heretofore been experienced in the manufacture of tubular insulators, particularly of the post type, to provide an insulator in which there is no danger of discharge through the central opening and one which can be economically manufactured. Wheres tubular insulator is left open to the atmosphere, moisture is apt to condense within the inside of the insulator giving rise to internal discharges which not only interfere with service, but are also apt to destroy the insulator. In order to overcome these difllcultlos, efforts have been made to manufacture insulators which are closed at one or both ends by means of some form of dielectric opening in such a way that internal discharges are avoided. The present invention overcomes these difllculties by providing a simple tubular insulator which is easy to manufacture and which is sealed with the internal opening filled or partially filled with a dielectric liquid which will prevent the possibility of discharges within the interior of the insulator.

In the embodiment of the invention shown in Fig. 1 the numeral ll designates a tubular insulator of dielectric material such as porcelain. The insulator may be provided with any desired form of flanges II or may be made plain, if preferred. The surface of the insulator adjacent the ends is suitably sanded or roughened, as indicated at H, and the portion of the roughened surface on the opposite ends of the insulator is preferably coated with metal by any suitable process. One method of providing such a coating is disclosed in the patent to Arthur 0'. Austin, No. 1,536,749, dated May 5, 1925. After the end surfaces of the tube have thus been coated a metal disc I3 is applied to one end of the tube and soldered to the coated surface. In applying the disc the surfaces to be united may first be given a coat of solder and then after the disc is placed it may be heated sufficiently to "sweat the disc to the end of the insulator, thus forming a hermetic seal for the end of the opening covered by the disc. The opening in the insulator is then partially filled with oil or other dielectric material ll which can be poured into the opening. A liquid material is preferable, but any suitable insulating compound may be used. After the interior of the insulator is thus filled with insulating material a second disc 15 is applied to the upper end of the insulator and also soldered in place in a manner similar to the application of the disc it.

It will be noted that the discs I3 and ii are each provided with inwardly extending electrodes i8 and I! which form controls for the dielectric field extending between the terminal caps I8 and is which are secured to the ends of the insulator by cement 20 after the discs have been soldered in place. A gas or air cushion 2| is left at the upper end of the insulator above the surface level of the dielectric liquid H to provide for expansion and contraction of the liquid for temperature changes. The electrode l1 preferably extends beneath the surface of the liquid ll so that possibility of discharge between the two electrodes is avoided. The electrodes thus control the dielectric field and reduce the danger of external discharge between the terminal caps, or in other words, raise the fiashover voltage of the insulator. Danger of discharge through the center of the insulator between the electrodes II and II is avoided because of the high dielectric strength of thefillingliquid l4. Theoilorotherinsulating liquid within the insulator is entirely protectedfromlightandairsothatitwillretainits dielectric properties without deterioration for an indefinite period of time. A tubular insulater is thusprovidedwhichissimpieandeconomicalto manufacture and in which the manufacturing lossesarereducedtoaminimumandyettheinsulatorhsshlghslectricalandmechanicalefiiciencyandexceptionaliy long lifesincethereis nothing about the insulator to deteriorate with time. The insulator, as shown in the drawing, is provided with fittings adapting it for use as a post, but it will be understood that with suitable fittingsthisformoftheinventionmaybeusedas a suspension, strain, or other insulator intended for use in an upright position. The form of the invention showninl'igs.2and3niaybeused equally well at any angle. while the form shown in Fig. 4 is especially suitable for horizontal use although it may also be used in other positions.

In the form of the invention shown in Fig. 2 the upper end of the insulator is provided with an expansion bellows II which communicates withtheexteriorof the insulatorsothatitis free to expand and contract to accommodate expansion and contraction of the liquid, which in this form may completely fill the sealed in space within the interior of the insulator. The bellows forms a complete seal for the upper end of the insulator, since it is provided with a circumferential fiange 28 which overlaps the upper end of the insulator and is soldered to the end surface of the dielectric member in a manner similartothediscs II and llinl ig. 1. Agasket lsmaybeappliedtothesm'faceofthedisc 28 during application of the cap II to exclude the cement I. from the interior of the bellows 22. The bellowsitself forms a flux distribution member which performs the fimction of the electrode II in Fig. i. The lower end of the bushing may be similar to that shown in Fig. 1.

In the form of the invention shown in Pig. 3, instead of a bellows 22, a flexible diaphragm II is employed having its periphery soldered to the end of the dielectric member as in the previously described forms. The diaphragm Il may be provided with an electrode It to serve as a fiux control.

In the form of the invention shown in Figs. 4 and 5, the opening through the center of the tube, instead of being of uniform diameter, has a smaller portion 21 extending through the central portion of the body with enlargements ll and II at each end of the insulator. 'Ihe main portion 21 of the opening is preferably no larger than is required for easy manufacture and safe drying of the porcelain. 'Ihe ends of the insulator may be sealed by metal discs it, as shown in the previously described forms, or may be sealed by porcelain discs II as shown in Fig. 4, having beveled edges It to which glase is applied before firing so that during firing the disc will be hermetically sealed in recesses in the ends of the dielectric tube. One of the discs 8| is preferably provided with a perforation it which extends only partially through the disc during the firing operation, but which may be broken completely through after the firing is completed to permit filling of the recess within the insulator. The operation may be similar to am disclosed in Patent 2,142,422 to John .1'.

ofliquidbeingsuch thatwheniheinsulatoris in a horizontal position the enflre central portion 21 will be filled with the liquid, but largements II and II at opposite ends insulator will be only parflally filled so leave pockets of air or gas to accommodate expansion and contraction of the liquid. After proper amount of liquid has been placed insulator, the opening it may be sealed metal disc 14 soldered over the opening metallised surface on the face of the The end caps It and II are cemented to ends of the insulator, as described in connection with Fig. 1. Instead of porcelain discs II and Ii the ends of the insulator may be closed by metal discs provided with fiux control electrodes It like those in Fig.1.

I claim:

1. An insulator comprising end fittings, a tubular dielectric member connecting said nttings and secured to said fittings for transmitting the mechanical load on said insulator from one of said fittings to the other, said dielectric member having imperforate metal discs soldered to the opposite ends thereof, hermetically sealing the opening in said insulator, a dielectric liquid d sposed within said ope ing and metal electrodes secured to said discs and and extending inwardly toward each other but separated from each other by the dielectric filling liquid in said opening, said filling liquid forming a continuous barrier across the space between said electrodes, the spacing between electrodes and the dielecfic strength of dthe filling liquid being suihcient remove any nger of discha e center of the insulator. m thrown the 2. An insulator comprising a tubular dielectric member, fittings secured to opposite ends of said member, means for hermetically closing the opposite ends of the opening in said insulator, a dielectric liquid disposed within said insulator and partially filling said opening but providing a cushion space therein and flux control electrodes projecting inwardly at each end of said opening, the inner ends of said electrodes being immersed in said dielectric liquid, said liquid forming a continuous barrier across the space between the adjacent ends of said electrodes.

3. An insulator comprising a porcelain tube having a central opening extending therethrough, separately formed closure members for the ends of said opening, said closure members being hermetically sealed to said tube at the opposite ends of said opening, fiux control electrodes extending inwardly from the pposite ends of said opening but having their inner ends spaced away from each other, a dielectric liquid disposed in said opening and forming a continuous barrier across the space between the adjacent ends of said electrodes, the ends of said electrodes being immersed in said liquid to prevent internal discharge between said electrodes, said liquid only partially filling said opening to provide for expansion and contraction of said liquid within said opening and metallic fittings secured to the opposite ends of said tube, the mechanical load on said insulator gag transmitted between said fittings by said 4. An insulator comprising a tubular dielecuric member, insulating liquid disposed in the opening in said dielectric member and partially filling said opening but leaving a. portion thereof not filled with said liquid to provide for expansionand contraction of said liquid due to temperature changes, said opening being of substantially uniform diameter throughout its middle portion and having an enlarged portion formed in the dielectric material of said member at one end of said opening, the liquid in said opening being sufllcient to fill the middle portion of said opening of uniform diameter to form a barrier between opposite ends of said dielectric member, irrespective of the position of said dielectric member.

5. An insulator comprising a tubular dielectric member having an opening therethrough, said opening having a central restricted portion of substantially uniform diameter and enlarged end. portions formed in the dielectric material of said member, means for hermetically sealing the ends of said opening and a dielectric liquid disposed in said opening but only partially filling the same to provide for expansion and contraction thereof due to temperature changes, the amount of liquid in said opening being sufllcient to fill the central restricted portion thereof and enough of the enlarged end portions to bring the surface level of said liquid above the ends of said restricted portion when said insulator is disposed horizontally.

WADE H. BURLESON. 

